The Pompadour is Louis XVI — fluted Corinthian pilasters, mirrored panels in gilded frames, a ceiling painted with scenes of love. Treat it as a set that is already built.

The room does the opulence for you. What is left to decide is which century it is, who is in it and what they are doing. That gilding will play Versailles, a Venetian palazzo, a Belle Époque supper club or a jeweller’s window, and none of it needs a flat built.

The room takes 250 for a reception, 110 for dinner, and 80 once you want a dance floor. Work out which of those you need early.

176 square metres is generous for people standing with a glass and tight for people sitting at rounds with waiters working between them. If you need 150 seated, this is not the room.

The ceiling is three metres and the chandelier comes down to 2.10. It is listed, so there is nothing to rig from.

That rules out aerial work and tall installations. Everything happens at the level the guests are at: the tables, the floor, the walls and the light.

The brochure calls the terrace large. It is 6.3 square metres, with patio heaters, through double doors at the end of the ballroom, looking down Regent Street.

It is a good place to step outside for air, a photograph or a quiet word. It will not take a bar, a band or a queue.

Three things in the brochure matter more than the décor.

Three-phase power in the ballroom. A proper lighting rig and a working kitchen, with no generator in the street. On Regent Street you could not put one there.

Triple glazing. The windows are quiet in both directions, so you can be loud at eleven o’clock in the middle of the West End.

A midnight licence, with an extension to 1am on request. Ask for it early.

Queensberry is the second big room: 141 square metres, 150 standing, 200 theatre, floor-to-ceiling windows over Piccadilly Circus, blackout curtains, and the lights and sound on a touchscreen. It is the room for the part of the day that needs a screen.

Then the small ones. Mayfair and Soho at about 40 each. Nicols at 20. Nash, a ten-seat boardroom. The Domino Room seats 60 for dinner. Ziggy’s is a Bowie-inspired bar for 50. The Gallery sits above the lobby and takes 160 with Ziggy’s alongside it.

Those are the rooms a producer uses all day: a green room, somewhere for wardrobe, somewhere to brief the cast, somewhere to put a client when something runs late.

These are not packages. They are five directions we would take this building, each drawn from a world we already design, and each one sized to a room in it.

Alex Dilling at Hotel Café Royal holds two stars and looks out over Regent Street. Albert Adrià’s Cakes and Bubbles is here. So is the Café Royal Grill.

That changes how we work. At a house or a hall we design the food with everything else and bring the kitchen in. Here the kitchen is already one of the reasons people come, so the job is to write the menu into the story.

Hotels price differently from houses. Before we could quote, we would ask four things.

Standing or seated. It changes the room, the number and a lot of the budget.

How late. Midnight, or the extension to one.

What is being built. The brochure prices the integrated AV as an extra. Everything past that is production.

How many rooms. A ballroom on its own is one figure. A ballroom plus a green room, a bar afterwards and somewhere for the crew is another.